release notes, perf-tuning: fix gPRC typo to gRPC

[yahonda]

What is changed, added or deleted? (Required)

Fixes a recurring misspelling of "gRPC" as "gPRC" across several release notes and the performance tuning guide:

• releases/release-2.0.6.md
• releases/release-4.0.16.md
• releases/release-5.0.6.md
• releases/release-5.1.4.md
• releases/release-6.1.0.md
• releases/release-6.1.3.md
• performance-tuning-methods.md (3 occurrences)

Found while reviewing CodeRabbit feedback on JA translation PR #23599 — the JA translations correctly mirrored this EN typo, so fixing it at the source here instead of diverging the translation.

Which TiDB version(s) do your changes apply to? (Required)

• master (the latest development version)

What is the related PR or file link(s)?

N/A

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

Summary by CodeRabbit

• Documentation
  • Corrected multiple occurrences of the “gPRC” typo to “gRPC” across performance documentation and release notes.
  • Clarified references to TiKV latency, Raft log replication, firewall fixes, TiCDC improvements, and gRPC message settings.

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⚙️ Run configuration

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📥 Commits

Reviewing files that changed from the base of the PR and between bc98972 and 103fa7e.

📒 Files selected for processing (3)

• releases/release-4.0.16.md
• releases/release-5.0.6.md
• releases/release-5.1.4.md

📝 Walkthrough

Walkthrough

The changes correct misspelled gRPC references in one performance document and six release notes. No exported or public entities change.

Changes

Documentation terminology corrections

Layer / File(s)	Summary
Performance documentation terminology performance-tuning-methods.md	Corrects three gPRC references in TiKV latency, Raft log replication, and duration descriptions.
Release note terminology releases/release-2.0.6.md, releases/release-4.0.16.md, releases/release-5.0.6.md, releases/release-5.1.4.md, releases/release-6.1.0.md, releases/release-6.1.3.md	Corrects six misspelled protocol references in historical firewall, TiCDC, TiKV, and TiDB release notes.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Merge Risk: ⚪ Minimal · up to bc989

This documentation-only PR corrects gPRC to gRPC across release notes and performance guidance. A minor wording consistency correction remains in three bullets, with no runtime or production impact; the PR is otherwise merge-ready after normal review.

Suggested reviewers: qiancai

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely identifies the main change: correcting the recurring “gPRC” typo to “gRPC” in release notes and performance-tuning documentation.
Description check	✅ Passed	The description explains the changes, lists the affected files, identifies the applicable version, and records that no special change category applies. It omits the AI agent involvement section, but t…
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Description check

Explanation

The description explains the changes, lists the affected files, identifies the applicable version, and records that no special change category applies. It omits the AI agent involvement section, but the required information is otherwise complete.

Full details: Docstring Coverage

Explanation

No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0 files. (7 skipped: 7 unsupported.)

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 57546f99-ca8d-4877-8603-805055adf5da

📥 Commits

Reviewing files that changed from the base of the PR and between ff98075 and bc98972.

📒 Files selected for processing (7)

• performance-tuning-methods.md
• releases/release-2.0.6.md
• releases/release-4.0.16.md
• releases/release-5.0.6.md
• releases/release-5.1.4.md
• releases/release-6.1.0.md
• releases/release-6.1.3.md

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